Many electronic devices include some type of user input device, including, for example, buttons, slides, scroll wheels, and similar devices or user-input elements. Some devices may include a touch sensor that is integrated or incorporated with a display screen. The touch sensor may allow a user to interact directly with user-interface elements that are presented on the display screen. However, some traditional touch sensors may only provide a location of a touch on the device. Other than location of the touch, many traditional touch sensors produce an output that is binary in nature. That is, the touch is present or it is not.
In some cases, it may be advantageous to detect and measure the force of a touch that is applied to a surface to provide non-binary touch input. However, there may be several challenges associated with implementing a force sensor in an electronic device. For example, temperature fluctuations in the device or environment may introduce an unacceptable amount of variability in the force measurements. Additionally, if the force sensor is incorporated with a display or transparent medium, it may be challenging to achieve both sensing performance and optical performance in a compact form factor.